Re: [Sipping] Possible Solution to HERFP

[Rohan Mahy <[e-mail]>]

Hi Jeroen,

In order to get the best user experience, the proxy should not have to
introduce an artificial delay so that the UAC can get (and possibly act
on) a repairable error.  For example, if branch #4 is the best possible
contact to reach me, but it responds with a 401 or a 415 or a 420,
delaying this until the proxy has heard from all branches, even for a few
moments, prevents the UA from getting the "best" branch.

thanks,
-rohan

On Mon, 18 Jul 2005, Jeroen van Bemmel wrote:

> Rohan,
>
> About the HERFP issue. I was not involved in earlier discussions, so I
> apologize if I am repeating something that was already said
>
> What if HERFP was addressed similar to how a proxy handles multiple 401+407
> responses: all repairable errors are collected and returned as one final
> response ( "4xx multiple responses" with the proxy generating a to-tag). The
> UA could then retry as its sees fit. Each error returned in this way should
> include an address to use to contact that specific entity only. The response
> body would probably be a good place for this collection of mayhem
>
> To address the potential long waiting for some ringing endpoints that block
> forwarding of repairable errors, the UAC could simply include an 'Expires'
> header in the original INVITE, and/or maybe a special 'HERFP timeout' value
> to tell the proxy to CANCEL ringing things and return the best final
> response(s) at that point instead.
>
> To address 2xx responses from hiding other alternatives, the proxy could
> append information about the pending repairable errors to the 2xx response
> before forwarding (for this case perhaps some header would be better than in
> the body). That would give the UAC an opportunity to try those other
> options. If some other branches have not returned yet, perhaps the proxy
> could append a header stating that ( i.e. "Proxy-HERFP-Pending: 3" )
>
> Regards,
>
> Jeroen
>
> ----- Original Message -----
> From: "Rohan Mahy" <[e-mail]>
> To: "'sipping' WG" <[e-mail]>
> Cc: "Rohan Mahy" <[e-mail]>
> Sent: Saturday, July 09, 2005 4:41 AM
> Subject: [Sipping] Possible Solution to HERFP
>
>
> > Hi Folks,
> >
> > I just submitted a new individual I-D that describes a possible  solution
> > to the Heterogeneous Error Response Forking Protocol.  Until  it appears
> > in the archives, you can find it here:
> >
> > https://scm.sipfoundry.org/rep/ietf-drafts/rohan/herf-fix/draft-mahy-
> > sipping-herfp-fix-00.txt
> > https://scm.sipfoundry.org/rep/ietf-drafts/rohan/herf-fix/draft-mahy-
> > sipping-herfp-fix-00.html
> >
> > thanks,
> > -rohan
> > (as an individual)
> >
> >
> > _______________________________________________
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> > This list is for NEW development of the application of SIP
> > Use [e-mail] for questions on current sip
> > Use [e-mail] for new developments of core SIP
>


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